loseit-mcp

An MCP server and CLI for logging food to Lose It!.

⚠️ Unofficial. Lose It! publishes no public API. This talks to the private GWT-RPC endpoint used by the Lose It! web app, so it can break whenever they ship a new web build.

Tools

log_custom_food exists because updateFoodLogEntry carries the food's name, brand, and nutrient map inline — so an entry can describe a food the database has never heard of. Use it for restaurant meals, homemade dishes, or any portion where forcing a database match would distort the numbers.

Related MCP server: nutrition-mcp

Setup

uv sync
cp .env.example .env   # then fill in your credentials

Configuration

Settings resolve in priority order: CLI flags → environment → .env → JSON config file → defaults.

* Not required if LOSEIT_TOKEN is set.

.env is gitignored. The session token is cached at ~/.config/loseit-mcp/session.json with owner-only permissions and refreshes automatically when it expires.

Running the server

loseit-mcp serve                                  # stdio (default)
loseit-mcp serve --transport streamable-http --port 8000

Register the stdio server with an MCP client:

{
  "mcpServers": {
    "loseit": {
      "command": "uv",
      "args": ["run", "loseit-mcp", "serve"],
      "cwd": "/absolute/path/to/loseit-mcp"
    }
  }
}

To host one server for multiple accounts, see DEPLOYMENT.md.

CLI

The same operations are available directly, which is the easiest way to test:

loseit-mcp search "greek yogurt" -n 5
loseit-mcp describe <food_id>
loseit-mcp diary 2026-07-25
loseit-mcp log <food_id> -m lunch -a 120 -u g
loseit-mcp log-custom "Caesar Salad" 620 -m lunch -b "Gastrohub" -p 46 -c 18 -f 40
loseit-mcp weigh 199.2
loseit-mcp weights -n 14
loseit-mcp delete <entry_id> -d 2026-07-25

Add --dry-run to either log command to preview the math without writing, and --json for machine-readable output.

Two more, for hosted deployments:

loseit-mcp gen-secret                      # a secret for LOSEIT_URL_SECRET
loseit-mcp enroll https://<host>           # get a credential URL for a client

A hosted deployment also serves a self-service enrollment page at /: someone enters their Lose It! email and password and gets their own MCP URL back, ready to paste into Claude, ChatGPT, or any other MCP client. Credentials are checked against Lose It before a URL is issued, so a typo fails immediately instead of producing a link that silently doesn't work.

The page is a single self-contained document under a strict CSP — no external scripts, styles, or fonts — so nothing but Lose It ever sees the credentials. Nothing is stored: the password is used once, in memory, and then encrypted into the URL itself, which is why there is no database and no account system.

Notes

• Deleting writes a recoverable copy to local trash before the wire call.

• When Lose It changes their private API, tools return an explanation of what broke and what the operator needs to refresh, rather than a decoder traceback — see errors.py.

• Hosted deployments rate-limit per client address and per credential, since an address alone is a weak identity behind a NAT pool. Enrollment adds a third limit, per email address, so verifying credentials can't be used to guess them.

• /healthz reports the running version and commit, so you can tell what is actually deployed without reading logs.

• Weights carry no unit over the wire; the number is interpreted in whatever unit the account displays (lb or kg).

• saturated_fat_g is not recorded. The upstream SDK's payload builder filters that nutrient ordinal out, so log_custom_food reports it in an ignored_nutrients field rather than claiming to have logged it. Every other macro goes through.

• Weight history is fetched in windows and bisected further when a response is too large for the SDK decoder — an unchunked year-long query would otherwise silently return "no weigh-ins".

• Relative dates (today / yesterday) resolve in the account's timezone, not the host's, so a server in another region doesn't log to the wrong day.

• Fractional portions of database foods can display a misleading unit (half a banana rendering as "1/4 Each") because the server's canonical serving count differs from the food's native unit. Calories stay correct, but log-custom is the more predictable route for odd portions.

Architecture

The GWT-RPC wire format is handled by the phitoduck/lose-it SDK. This project adds email/password authentication (the SDK expects you to supply a JWT yourself, and its browser-cookie import does not support Windows), the custom-food logging path, weight recording via saveRecordedWeight (captured from the web app's weigh-in widget), and the MCP server and CLI layers.

License

0BSD — the BSD Zero Clause License. Use it, change it, ship it, sell it. No attribution, no notice, no conditions of any kind.

This is deliberate. If FitNow (the makers of Lose It!) want any part of this, they should take it and treat it as their own — no permission needed, nothing to negotiate, no obligation to credit me. The same goes for anyone else.

Two things a license cannot do, stated plainly:

• Trademark is separate. "Lose It!" is a registered trademark of FitNow, Inc. This project is unofficial and unaffiliated; the license grants no rights in their marks.

• Dependencies keep their own terms. They are all permissive (MIT, BSD-3, Apache-2.0), but the lose-it SDK is MIT and asks that its copyright notice be preserved. Anyone vendoring this code should either keep that notice or replace the dependency.